Coating of carboxyl (meth)acrylic copolymer or polyester and urea anti-sag agent prepared in polyepoxide

ABSTRACT

Coating composition suitable for multilayer lacquering, containing, in addition to organic solvent, anti-sagging agents, optionally pigments, extenders and additives, a binder/crosslinkin agent system containing 
     A) from 20 to 80 wt. % of carboxyl-functional (meth)acrylic copolymers and/or carboxyl-functional polyesters having an acid number of from 20 to 300, 
     B) from 20 to 80 wt. % of epoxy-functional crosslinking agents, the percentages by weight of A) and B) adding up to 100 wt. %. 
     C) from 0 to 30 wt. % of polymer polyol C), based on the sum of the weights of A) and B), 
     E) from 0 to 20 wt. % of further crosslinking agents, based on the sum of the weights of A, B, and C), 
     F) from 0 to 10 wt. % of monoepoxides, based on the sum of the weights of A) and B), and 
     D) as anti-sagging agents, from 0.1 to 3 wt. %, based on the resin solids, of solid, finely divided urea compounds D) which have previously been prepared in the presence of at least a portion of the epoxy-functional crosslinking agent B) and which are insoluble in the coating compositions, 
     all percentages are by weight being based in each case on the solids.

The invention relates to coating compositions and their use in theproduction of multilayer lacquer coatings, for example in the automotivesector, especially in the production of two-layer lacquer coatings ofthe base lacquer/clear lacquer type.

Coating compositions that are based on a combination of anepoxy-functional component and a carboxyl-functional component and thatcure with the formation of esters are known. They are distinguished bythe fact that the coatings produced therefrom and stoved have goodresistance to chemicals and acids, and they are therefore especiallysuitable as clear lacquers or finishing lacquers in the serieslacquering of motor vehicles.

For example, there is known from DE-A-30 22 996 a stoving lacquer inwhich polymers containing carboxyl groups, such as, for example,(meth)acrylic copolymers based on acrylic acid or methacrylic acid, andacrylate resins containing glycidyl groups are mixed to form a curablecomposition.

DE-A-42 37 658 also describes stoving lacquer systems based oncomponents containing carboxyl groups and components containing epoxygroups. In this case, the carboxyl groups are chain-lengthened withlactone in order to increase the reactivity.

The visual aesthetic effect of base lacquer/clear lacquer two-layerlacquer coatings is influenced essentially by the quality of the clearlacquer layer. Ideally, the structure of the clear lacquer layer is thesame on horizontal and vertical surfaces of a three-dimensionalsubstrate, for example a motor vehicle body. However, the describedideal case cannot readily be achieved in practice. For example,differences in the surface structure or in the flow of the outer clearlacquer layer may occur since, after application and especially duringthe heating phase of the stoving process, the clear lacquers tend to runor sag on surfaces that are outside the horizontal as a result of atemperature-related fall in the viscosity. That risk is greater, thegreater the thickness of the clear lacquer layer.

It is known from DE-C-27 51 761 and EP-A-0 198 519 to use particularurea compounds as additives in aminoplastic-resin-curing stovinglacquers based on hydroxyl-functional binders, in order to counteractundesired sagging phenomena of the lacquer on stoving. It isadditionally known from EP-A-0 192 304 to use urea compounds asanti-sagging agents in lacquers that contain hydroxyl-functional bindersand aminoplastic resins or free or blocked polyisocyanates ascrosslinking agents. The resistance to chemicals, especially theresistance to acids, of the stoved coating layers produced from thosecoating compositions is in need of improvement.

The object of the invention is to provide coating compositions thatexhibit a reduced tendency to sag even when applied in relatively greatlayer thicknesses and that, in the stoved state, result in coatingshaving good resistance to acids and chemicals. The coating compositionsare to be suitable especially as stoving coating compositions for theproduction of the outer clear lacquer or finishing lacquer layer of amultilayer lacquer coating.

The object is achieved by means of curable coating compositionscontaining binders and crosslinking agents, one or more organicsolvents, anti-sagging agents and, optionally, pigments and/or extendersand, optionally, further additives conventionally employed in lacquers,wherein there are present as binders from 20 to 80 wt. % of one or morecarboxyl-functional components A) selected from carboxyl-functional(meth)acrylic copolymers and/or carboxyl-functional polyesters, thecarboxyl functionality of which corresponds in each case to an acidnumber of from 20 to 300 mg of KOH/g, and from 20 to 80 wt. % of one ormore epoxy-functional crosslinking agents B), the percentages by weightadding up to 100 wt. % which coating compositions are characterised inthat they contain as anti-sagging agents from 0.1 to 3 wt. % based onthe resin solids, of one or more solid urea compounds D) which havepreviously been prepared in the presence of at least a portion of theepoxy-functional crosslinking agent(s) B) and which are insoluble in thecoating composition, all percentages by weight in each case being basedon the solids content.

The binder/crosslinking agent system of the coating compositionsaccording to the invention contains components A) and B) as theessential components and, if desired, the optional components C) and/orE) and/or F) mentioned below. For example, the coating compositionsaccording to the invention may contain only components A) and B) as thebinder/crosslinking agent system, or the binder/crosslinking agentsystem of the coating compositions according to the inventionadditionally contains the optional components C) and/or E) and/or F).The resin solid of the coating compositions according to the inventionis formed from the sum of the resin solids or the non-volatile portionsof components A), B) and the optional components C), E) and F) mentionedbelow.

Curing of the coating compositions according to the invention is basedon the chemical reaction which takes place during stoving between thegroups of components A) and B) that are complementarily reactive withrespect to one another; it is an addition of the carboxyl groups to theepoxy groups with formation of carboxylic acid ester compounds.

The present invention provides curable coating compositions with whichthe stated object can be achieved. It was in no way to be expected thatthe object would be successfully achieved when the synthesis of the ureacompounds D) from corresponding amine and isocyanate compounds, asdiscussed in greater detail below, is carried out in the presence ofepoxy-functional crosslinking agents B). Surprisingly, the object issuccessfully achieved even though the urea compounds D) are prepared inthe presence of epoxy-functional crosslinking agents B) that arereactive towards amine compounds. It is advantageous that theepoxy-functional crosslinking agents B), which are themselves aconstituent of the coating composition according to the invention, canbe used as the reaction medium for the synthesis of the urea compoundsD). It is not necessary to synthesise the urea compounds D) in aseparate reaction medium, addition of which to the binder/crosslinkingagent system containing components A) and B) of the coating compositionsaccording to the invention would possibly be undesirable and optionallyeven have an adverse effect.

The coating compositions according to the invention contain as componentA) one or more carboxyl-functional components A). Thecarboxyl-functional component A) of the coating compositions accordingto the invention is carboxyl-functional (meth)acrylic copolymers and/orcarboxyl-functional polyesters, the carboxyl functionality of whichcorresponds in each case to an acid number of from 20 to 300 mg ofKOH/g. The carboxyl-functional (meth)acrylic copolymers and/orcarboxyl-functional polyesters may be urethanised and/or modified byreaction with lactones.

The carboxyl-functional (meth)acrylic copolymers of component A)optionally containing urethane groups preferably have a number-averagemolecular weight (Mn) of from 1000 to 30,000 g/mol. Thecarboxyl-functional polyesters of component A) optionally containingurethane groups preferably have a calculated molecular weight of from500 to 4000 g/mol. The acid number is in each case from 20 to 300 mg ofKOH/g, preferably from 30 to 250 mg of KOH/g.

In the preparation of the carboxyl-group-containing (meth)acryliccopolymers or polyesters of component A), each of which may optionallycontain urethane groups, the carboxyl groups may be introduced directlyby the use of structural units containing carboxyl groups. Examples ofsuitable monomers containing carboxyl groups that may be used for thesynthesis of carboxyl-group-containing (meth)acrylic copolymers areunsaturated carboxylic acids, such as, for example, acrylic,methacrylic, itaconic, crotonic, isocrotonic, aconitic, maleic andfumaric acid, half-esters of maleic and fumaric acid, and carboxyalkylesters of (meth)acrylic acid, for example beta-carboxyethyl acrylate andadducts of hydroxyalkyl (meth)acrylates with carboxylic acid anhydrides,such as, for example, phthalic acid mono-2-(meth)acryloyloxyethyl ester.

In the present description and the patent claims, the term (meth)acrylicis used. This means acrylic and/or methacrylic.

In the preparation of (meth)acrylic copolymers or polyesters ofcomponent A) containing carboxyl groups and optionally containingurethane groups, it is, however, also possible first to synthesise apolymer containing hydroxyl groups and optionally already also carboxylgroups and to introduce some or all of the carboxyl groups in a secondstep by reaction with carboxylic anhydrides. In that procedure, it ispossible to use such relative proportions that, if necessary, sufficienthydroxyl groups remain to allow urethanisation to be carried out.

Carboxylic acid anhydrides suitable for addition to thehydroxyl-group-containing polymers, which may already contain carboxylgroups, are the anhydrides of di- and poly-carboxylic acids, such as,for example, preferably phthalic, tetrahydro-, methylhexahydro- andhexahydro-phthalic anhydride.

Monomers suitable for the introduction of hydroxyl groups into the(meth)acrylic copolymers of component A) optionally containing urethanegroups are, for example, hydroxylalkyl (meth)acrylates, such as, forexample, hydroxyethyl (meth)acrylate, as well as the hydroxypropyl(meth)acrylates and hydroxybutyl (meth)acrylates which are isomeric withrespect to the position of the hydroxyl group.

There may also be used as the hydroxyl-functional component at leastpartly a reaction product of (meth)acrylic acid with the glycidyl esterof a carboxylic acid having a tertiary alpha-carbon atom. Glycidylesters of highly branched monocarboxylic acids are obtainable, forexample, under the trade name “Cardura”. The reaction of the acrylicacid or methacrylic acid with the glycidyl ester of a carboxylic acidhaving a tertiary alpha-carbon atom may take place before, during orafter the polymerisation reaction.

In the preparation of the (meth)acrylic copolymers of component A) it ispossible to use in addition to the above-mentioned monomers also furtherolefinically unsaturated monomers, especially those which contain nofurther functional groups besides an olefinic double bond. The choice ofthe further olefinically unsaturated monomers is not critical; theolefinic monomers with or without further functional groupsconventionally employed for polymerisation may be used. The monomers arepreferably so chosen in the manner known to the person skilled in theart that their incorporation does not lead to undesirable properties ofthe copolymer.

There are suitable as further olefinically unsaturated monomers, forexample, especially alkyl esters of (meth)acrylic acid, such as, forexample, methyl (meth)acrylate, ethyl (meth)acrylate, propyl(meth)acrylate, butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl(meth)acrylate, tert.-butyl (meth)acrylate, hexyl (meth)acrylate,cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl(meth)acrylate, hexadecyl (meth)acrylate.

Instead of the above-mentioned (meth)acrylic acid alkyl esters ortogether therewith, further olefinically unsaturated monomers may beused for the preparation of (meth)acrylic copolymers of component A),the choice of those monomers being largely dependent on the desiredproperties of the coating compositions in respect of hardness,elasticity, tolerability and polarity.

Examples of further suitable olefinically unsaturated monomers are thealkyl esters of maleic, fumaric, tetrahydrophthalic, crotonic,isocrotonic, vinylacetic and itaconic acids, such as, for example, thecorresponding methyl, ethyl, propyl, butyl, isopropyl, isobutyl, pentyl,amyl, isoamyl, hexyl, cyclohexyl, 2-ethylhexyl, octyl, decyl, dodecylesters.

There may also be used small amounts of monomers having at least twopolymerisable, olefinically unsaturated double bonds. The amount ofthose monomers is preferably less than 5 wt. %, based on the totalweight of the monomers.

Examples of such compounds are hexanediol di(meth)acrylate, ethyleneglycol di(meth)acrylate, butanediol di(meth)acrylate,hexamethylenebis(meth)acrylamide, trimethylolpropane tri(meth)acrylate,divinylbenzene and similar compounds.

Monovinylaromatic compounds are a further suitable component. Theypreferably contain 8 or 9 carbon atoms per molecule. Examples ofsuitable compounds are styrene, vinyltoluene, alpha-methylstyrene, aswell as the isomeric methylstyrenes. Vinyltoluenes and, especially,styrene are preferably used. The use of silane-modified monomers, suchas, for example, gamma-methacryloxypropyltrimethoxysilane, is alsopossible.

The preparation of the (meth)acrylic copolymers of carboxyl-functionalcomponent A) is effected by radical copolymerisation. It may proveadvantageous to add some of the monomers in a manner that is staggeredin terms of time.

For the preparation of the (meth)acrylic copolymers of component A), themonomers or the monomer mixture used may contain radical initiators. Ifradical initiators are not contained in the monomer mixture, they may beadded to the monomer mixture optionally staggered slightly with respectto one another in terms of time or they may be metered in separately.Polymerisation may then be continued for a prolonged period, for examplefor several hours. It is then possible to adjust the mixture to adesired solids content, for example of the order of from 30 to 80 wt. %,for example from 50 to 60 wt. %, with a suitable lacquer solvent. Thepreparation is carried out, for example, as a radical solutionpolymerisation in the presence of a radical initiator such as is knownto the person skilled in the art. Examples of radical initiators aredialkyl peroxides, diacyl peroxides, hydroperoxides, per-esters,peroxide dicarbonates, per-ketals, ketone peroxides; azo compounds, suchas 2,2′-azo-bis-(2,4-dimethyl-valeronitrile), azo-bis-isobutyronitrile,C—C-cleaving initiators, such as, for example, benzpinacol derivatives.

The polymerisation initiators are generally added, for example, in anamount of from 0.1 to 4 wt. %, based on the amount of monomersoriginally weighed in.

For the possible urethanisation of the carboxy-functionalised(meth)acrylic copolymers of component A), hydroxyl groups of thecarboxyl-functionalised (meth)acrylic copolymers of component A) may bereacted in a further reaction step with mono-, di-, tri- orpoly-isocyanates. Examples of isocyanates which can be used for theurethanisation are phenyl isocyanate as well as the polyisocyanatesmentioned by way of examples below in the description of the additionalcrosslinking agents E), and their defunctionalisation productsobtainable by reaction with less than stoichiometric amounts, based onthe isocyanate content, of monoalcohols. The amount of di-, tri- orpoly-isocyanates used for the urethanisation is chosen in the mannerknown to the person skilled in the art so that gelling is avoided. Ofcourse, it is also possible to urethanise hydroxyl-functional(meth)acrylic copolymers before carboxyl groups are introduced byreaction with acid anhydrides.

The polyesters of component A) containing carboxyl groups and optionallycontaining urethane groups can be synthesised by conventional methodsfrom aliphatic and/or cycloaliphatic di-, tri- or higher-hydricalcohols, optionally together with monohydric alcohols, and fromaliphatic, aromatic and/or cycloaliphatic carboxylic acids, especiallydicarboxylic acids, and higher-valent polycarboxylic acids. Examples ofsuitable alcohols are aliphatic diols, such as ethylene glycol,1,2-propanediol, 1,3-propanediol, 2,2-diethyl-1,3-propanediol, theisomeric butanediols, 1,5-pentanediol, 3-methyl-1,5-pentanediol,1,6-hexanediol, 2-ethyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol,1,4-dimethylolcyclohexane, polyhydric aliphatic alcohols, such asglycerol, trimethylolethane, trimethylolpropane, ditrimethylolpropane,pentaerythritol, as well as etherification products of diols andpolyols, for example di- and tri-ethylene glycol, polyethylene glycol,neopentyl glycol esters of hydroxypivalic acid.

Examples of suitable carboxylic acids are adipic acid, azelaic acid,1,3- and 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid,hexahydrophthalic acid, endomethyltetrahydrophthalic acid, the isomericphthalic acids and their anhydrides and their esterifiable derivatives.

Like the carboxyl-functional (meth)acrylic copolymers of component A)already described, the carboxyl-functional polyesters of component A)may be urethanised. The reaction conditions and the polyisocyanates thatcan be used are the same as in the case of the (meth)acrylic copolymers.Introduction of the urethane groups is possible by reaction of thecarboxyl- and hydroxyl-functional polyesters with mono-, di-, tri- orhigher-functional polyisocyanates.

It is also possible to introduce the urethane groups during thesynthesis of the polyesters themselves. That is effected by replacingdi- or tri-carboxylic acids wholly or partially by di- ortri-isocyanates.

The carboxyl groups of the carboxyl-functional (meth)acrylic copolymersand polyesters of component A) may be “chain-lengthened” with a lactone.The same applies to any hydroxyl groups contained in the (meth)acryliccopolymers and polyesters of component A). The “chain lengthening” isobtained by the addition, which proceeds with ring opening, of lactonesto the carboxyl and/or hydroxyl groups. In that process, terminal,exposed carboxyl and/or hydroxyl groups form. Preference is given to theaddition of lactones to carboxyl-functional (meth)acrylic copolymers andpolyesters of component A) that are free of OH groups. The addition ofthe lactone is preferably carried out as the last synthesis step in thepreparation of component A) in question. An example of a lactone that isparticularly preferably used is epsilon-caprolactone.

The curable coating compositions according to the invention contain ascomponent B) one or more epoxy-functional crosslinking agents. A portionor the total amount of the epoxy-functional crosslinking agents B)contained in the coating compositions according to the invention servesas the reaction medium in the preparation of the urea compounds D)discussed below.

The epoxy-functional crosslinking agents B) are, for example, compoundshaving at least two epoxy functions in the molecule and an epoxyequivalent weight of, for example, from 200 to 700, preferably from 250to 500 and especially from 300 to 400, in each case based on solidresin. The number-average molecular weight (Mn) is preferably from 200to 10,000 g/mol. The glass transition temperature is preferably from−20° C. to 70° C., particularly preferably from 0C to 50° C. and moreparticularly from 5° C. to 40° C. The upper limit is preferably up to50° C.

Examples thereof are conventional di- or polyepoxides, for examplepolyglycidyl ethers based on diethylene glycol, dipropylene glycol,polypropylene glycol, bisphenol A or triglycidyl ethers of glycerol.

Further examples of di- or poly-epoxides are those based on di- orpoly-glycidyl esters. Examples thereof are reaction products of1-hydroxy-2,3-epoxypropane with phthalic acid or terephthalic acid toform phthalic acid or terephthalic acid bis(2,3-epoxypropyl ester), or adiglycidyl ether of bisphenol A with trimellitic anhydride to formpolyesters, for example having a number-average molecular weight (Mn) offrom 500 to 2000.

Preferred components B) are epoxy-functional (meth)acrylic copolymers,especially glycidyl (meth)acrylate copolymers. There may be chosen asthe comonomers, for example, (meth)acrylic acid esters, such as, forexample, methyl, ethyl, butyl, isobutyl, ethylhexyl, cyclohexyl and/orlauryl (meth)acrylate, (meth)acrylic acid hydroxyalkyl esters, such as,for example, hydroxyethyl and/or hydroxypropyl (meth)acrylate, alsostyrene, vinyltoluene and/or alpha-methylstyrene, as well as allalpha,beta-unsaturated monomers as have already been described above inconnection with component A). The number-average molecular weight (Mn)may be, for example, from 1000 to 10,000, preferably from 2000 to 5000.Further copolymerisable glycidyl-functional monomers are, for example,(meth)allyl glycidyl ether or 3,4-epoxy-1-vinylcyclohexane. Thepreparation of the copolymers is carried out by means of radicalsolution polymerisation; it is known to the person skilled in the artand is carried out according to conventional methods.

In the preparation of the coating compositions according to theinvention, the relative proportions are preferably so chosen that thereis a molar ratio of carboxyl groups to epoxy groups of from 1:3 to 3:1between the carboxyl-group-containing component A) and the epoxycomponent B).

The coating compositions according to the invention may contain as aconstituent of their binder/crosslinking agent system from 0 to 30 wt. %of one or more polymer polyols C), based on the sum of the weights ofcomponents A) and B), in each case based on the solids content.

The polymer polyols C) optionally contained in the coating compositionsaccording to the invention are polymer polyols selected fromhydroxyl-functional polyesters, polyurethanes and/or (meth)acryliccopolymers other than components A) and B) which, besides the carboxylgroups or epoxy groups, contain hydroxyl groups. The polymer polyols C)have at least two hydroxyl functions in the molecule. In addition to thehydroxyl groups corresponding to a hydroxyl number of, for example, from30 to 350 mg of KOH/g, the polymer polyols C) may also contain carboxylgroups corresponding to an acid number of from 0 to less than 20 mg ofKOH/g. The polymer polyols C) preferably contain no further functionalgroups, especially no epoxy groups, besides the hydroxyl groups and thecarboxyl groups which may optionally be present.

The polymer polyols C) optionally used in the coating compositionsaccording to the invention are, for example, those having anumber-average molar mass (Mn) of from 500 to 10,000 and hydroxy numbersof from 30 to 350, preferably from 50 to 280, mg of KOH/g.

Examples of hydroxy-functional polyester resins or hydroxyl-functionalpolyurethane resins which may be used as polymer polyols C) in thecoating compositions according to the invention are conventionalpolyester or polyurethane resins, for example those having anumber-average molar mass (Mn) of from 500 to 5000, preferably from 1000to 3000, and hydroxy numbers of from 30 to 350, preferably from 50 to280, mg of KOH/g.

Examples of hydroxyl-functional (meth)acrylic copolymers which may beused as polymer polyols C) in the coating compositions according to theinvention are conventional (meth)acrylic copolymers, for example thosehaving a number-average molar mass (Mn) of from 1000 to 10,000 andhydroxy numbers of from 30 to 300, preferably from 50 to 250, mg ofKOH/g. The (meth)acrylic copolymers may have been prepared, for example,in the presence of oligomeric or polymeric polyester and/or polyurethaneresins, for example those as mentioned in the two preceding paragraphs.

In addition to components A) and B) and, optionally, C), the coatingcompositions according to the invention may also contain as aconstituent of their binder/cross-linking agent system one or moreadditional crosslinking agents E) other than A), B) and C), which permitadditional crosslinking involving hydroxyl groups, for example thehydroxyl groups optionally present in the binder system and/or formedduring stoving in the course of the epoxy/carboxyl addition reaction.The additional crosslinking agents are present in total amounts of from0 to 20 wt. %, based on the sum of components A) and B) and, optionally,C), in each case based on the solids content.

Examples of additional crosslinking agents E) are aminoplastic resins,especially melamine resins. Examples thereof are melamine resinsetherified by butanol or isobutanol, such as, for example, thecommercial products Setamin® US 138 or Maprenal® MF 610; melamine resinsetherified by both butanol and methanol, such as, for example, Cymel®254, melamine resins etherified by methanol, such as, for example,Cymel® 325, Cymel® 327, Cymel® 350 and Cymel® 370, Maprenal® MF 927, ormelamine resins of the hexamethoxymethylmelamine type, such as, forexample, Cymel® 301 or Cymel® 303.

Further examples of additional crosslinking agents E) are triazine-basedcomponents that crosslink with the formation of ester groups, especiallywith the formation of urethane groups (carbamic acid ester groups), suchas, for example, preferably tris(alkoxycarbonylamino)triazine.

Further examples of additional crosslinking agents E) are blockedpolyisocyanates, which can be prepared from free polyisocyanates byreaction with compounds containing an active hydrogen atom that areremovable again under the stoving conditions. Examples ofpolyisocyanates that can be used are especially cycloaliphatic andaliphatic polyisocyanates, such as tetramethylene diisocyanate,hexamethylene diisocyanate, 2,2,4-trimethylene diisocyanate, cyclohexane1,3- and 1,4-diisocyanate, isophorone diisocyanate, biscyclohexylmethanediisocyanate.

In addition to those simple isocyanates, isocyanates containing heteroatoms in the radical linking the isocyanate groups are also suitable.Examples thereof are polyisocyanates having carbodiimide groups,allophanate groups, isocyanurate groups, uretdione groups, urethanegroups, acylated urea groups and/or biuret groups.

Especially suitable are the known polyisocyanates which areconventionally employed in the production of lacquers, for examplemodification products of the above-mentioned simple polyisocyanatescontaining biuret, isocyanurate or urethane groups, especiallytris-(6-isocyanatohexyl)-biuret, the isocyanurate derived fromisophorone diisocyanate or hexane diisocyanate, or low molecular weightpolyisocyanates having urethane groups, as can be obtained by reactionof isophorone diisocyanate, used in excess, with simple polyhydricalcohols having a molecular weight in the range from 62 to 300,especially with trimethylolpropane. Of course, any desired mixtures ofthe mentioned polyisocyanates may also be used.

Suitable polyisocyanates are also the known pre-polymers having terminalisocyanate groups, as are obtainable especially by reaction of theabove-mentioned simple polyisocyanates, especially diisocyanates, withdeficient amounts of organic compounds having at least two groups thatare reactive towards isocyanate groups. In those known pre-polymers, theratio of isocyanate groups to hydrogen atoms that are reactive towardsisocyanate groups is preferably from 1.05 to 10:1, particularlypreferably from 1.1 to 3:1, the hydrogen atoms preferably originatingfrom hydroxyl groups. The nature of the starting materials used in thepreparation of pre-polymers having isocyanate groups and the relativeproportions thereof are, furthermore, preferably so chosen that thepre-polymers having isocyanate groups have an average NCO functionalityof from 2 to 4, preferably from 2 to 3, and a number-average molar massMn) of from 500 to 10,000, preferably from 800 to 4000.

There are used as masking agents compounds having an active hydrogenatom, for example selected from CH-acid compounds such as acetylacetoneor CH-acid esters such as, for example, acetic acid alkyl esters,malonic acid dialkyl esters, aliphatic or cycloaliphatic alcohols, suchas n-butanol, isopropanol, tert.-butanol, furfurol, 2-ethylhexanol,cyclohexanol; oximes, such as methyl ethyl ketoxime, acetone oxime,cyclohexanone oxime, acetophenone oxime, lactams, such asepsilon-caprolactam or 2-pyrrolidone, imidazoles, such as2-methylimidazole, pyrazoles, such as 2,3-dimethylpyrazole.

Further examples of additional crosslinking agents E) which may becontained in the coating compositions according to the invention areorganic compounds having at least two cyclic carboxylic acid anhydridegroups per molecule. The content of carboxylic acid anhydride groups(formally calculated as C₄O₃, molecular weight=96) in those compounds ispreferably from 5 to 88 wt. %, particularly preferably from 6 to 30 wt.%. There are suitable, for example, trimellitic anhydride esters ofethylene glycol, propylene glycol, diethylene glycol, triethyleneglycol, neopentyl glycol, glycerol or trimethylolpropane, preferablyprepared in a ratio of 1 mol of trimellitic anhydride per mol ofhydroxyl groups.

Further suitable polyanhydrides are, for example,benzophenonetetracarboxylic acid dianhydride and1,2,4,5-benzenetetracarboxylic acid dianhydride.

Particularly preferred polyanhydrides are copolymers of olefinicallyunsaturated monomers having as a statistical average at least two cycliccarboxylic acid anhydride groups per molecule. They are preferablycopolymers of maleic anhydride and/or itaconic anhydride withconventional monomers, as are described by way of examples in connectionwith component A), for example. Copolymers based on maleic anhydride,styrene and/or alkyl esters of acrylic and/or methacrylic acid areespecially suitable. The copolymers preferably have a number-averagemolecular weight (Mn) of from 1500 to 75,000, particularly preferablyfrom 2000 to 50,000.

The coating compositions according to the invention may also contain asa constituent of their binder/crosslinking agent system from 0 to 10 wt.% of monoepoxy compounds F), based on the sum of components A) and B),in each case based on the solids. The components F) are substances thatare substantially non-volatile under the stoving conditions; forexample, the volatile portion is preferably less than 1 wt. %, based onthe total amount of monoepoxide F). The calculated molar masses of themonoepoxides F) are above 150, and preference is given to such compoundshaving a number-average molecular weight (Mn) of up to 3000,particularly below 1000. In the case of the low molecular weights, thosecompounds may have a positive effect on the viscosity behaviour of thelacquers produced therewith since, when added to carboxyl groups ofcomponent A), they act almost as reactive diluents.

Examples of such compounds are, for example, reaction products of adiglycidyl compound, for example a diglycidyl ether, such as one mol ofdiglycidyl ether of bisphenol A and one mol of a saturated orunsaturated monocarboxylic acid such as acetic acid, propionic acid orisononanonic acid. Further examples are reaction products of di- orpoly-epoxides, such as, for example, polyglycidyl ethers based ondiethylene glycol, dipropylene glycol, polypropylene glycol having anumber-average molecular weight of up to 2000 and triglycidyl ethers ofglycerol and/or polyphenols, such as bisphenol A or F, with thementioned monocarboxylic acids.

Particular preference is given to the glycidyl ester of versatic acidhaving the commercial product name Cardura E from Shell AG.

When in the application-ready state, the coating compositions accordingto the invention have a solids content, formed by the resin solid of thebinder/crosslinking agent system, the urea compounds D) mentioned belowand further non-volatile constituents which may be present, of from 40to 70 wt. %. As volatile constituents they contain organic solvents,such as are conventionally employed, for example, for the production ofcoating compositions, for example lacquers. They may also be solventssuch as are used in the preparation of the individual components.Examples are glycol ethers, such as butyl glycol, butyl diglycol,dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether,ethylene glycol dimethyl ether; glycol ether esters, such as ethylglycol acetate, butyl glycol acetate, 3-methoxy-n-butyl acetate, butyldiglycol acetate, methoxypropyl acetate; esters, such as butyl acetate,isobutyl acetate, amyl acetate; ketones, such as methyl ethyl ketone,methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone;alcohols, such as methanol, ethanol, propanol, butanol; aromatichydrocarbons, such as xylene, Solvesso 100 (registered trade mark for amixture of aromatic hydrocarbons having a boiling range from 155 to 185°C.) and aliphatic hydrocarbons.

The coating compositions according to the invention contain from 0.1 to3 wt. %, preferably from 0.3 to 2 wt. %, particularly preferably from0.5 to 1.5 wt. %, based on the resin solids of the coating compositions,of one or more solid urea compounds D) which have previously beenprepared in the presence of at least a portion of the epoxy-functionalcrosslinking agent(s) B) and which are insoluble in the coatingcomposition, as anti-sagging agents, that is to say as agents that havea thixotropic action or bring about intrinsic viscosity, which have anadvantageous effect on the sagging behaviour of the coating compositionsaccording to the invention. They effectively prevent undesired runningor sagging of coating layers of the coating compositions according tothe invention applied to vertical surfaces.

The urea compounds D) are conventional anti-sagging agents, such as, forexample, urea compounds known from DE-C-27 51 761, EP-A-0 192 304 andEP-A-0 198 519.

The urea compounds D) are addition products of aromatic, araliphatic,cycloaliphatic or aliphatic diisocyanates and/or polyisocyanates derivedtherefrom (for example those of the isocyanurate type) and mono- and/orpolyamines having primary and/or secondary amino groups. The additionproducts may be defined low molecular weight compounds or oligomeric orpolymeric addition products. Preferred urea compounds D) are those inwhich polyisocyanate and amine have been reacted in a stoichiometricratio of from 0.7 to 1.5 primary and/or secondary amino groups perisocyanate group, particularly in a stoichiometric ratio of amino groupsto isocyanate groups of from 0.9 to 1.1:1. Special preference is givento the use of addition products of diisocyanates, preferably ofaliphatic or cycloaliphatic diisocyanates, and primary amines,preferably primary monoamines, as urea compounds D). The aliphatic orcycloaliphatic diisocyanates are preferably diisocyanates having asymmetrical structure.

The urea compounds D) used in the coating compositions according to theinvention are so selected that they are solid, particularly preferablycrystalline, substances. The particle sizes of the D) particles arepreferably from 0.1 to 20 μm. The solid or crystalline urea compounds D)preferably have a high solidification or melting point, which especiallyis above the stoving temperatures that prevail during stoving of thecoating compositions according to the invention, especially above 80°C., for example from 80 to 250° C. Special preference is given to theuse of the adduct formed from 1,6-hexane diisocyanate and benzylamine ina molar ratio of 1:2 as the urea compound D) in the coating compositionsaccording to the invention.

The urea compounds D) can be prepared in the conventional manner by theaddition of amines having primary and/or secondary amino groups topolyisocyanates. It is possible to add the amine to the polyisocyanateor the polyisocyanate to the amine, or the reactants are addedsimultaneously; addition of the amine to the polyisocyanate ispreferred. The preparation takes place, for example, at temperatures offrom 20 to 80° C. in the presence of at least a portion of theepoxy-functional crosslinking agent(s) B) contained in the coatingcomposition according to the invention, that is to say in the presenceof a portion or all of the epoxy-functional crosslinking agent(s) B)present in the coating composition according to the invention. If thecoating composition according to the invention contains more than oneepoxy-functional crosslinking agent B), the preparation may take place,for example, in one of those epoxy-functional crosslinking agents B).When preparing the urea compounds D) it is advantageous to ensure thatthe reaction system is mixed thoroughly, for example by vigorousstirring, by the use of a dissolver or by carrying out the additionreaction in or using a rotor-stator unit. The procedure is preferablysuch that the urea compounds D) that form precipitate or crystallise outas a finely divided solid in the epoxy-functional crosslinking agentcomponent B) or the organic solution thereof (for example in one of thesolvents mentioned above for the coating compositions), for exampleduring or after completion of the addition reaction, for example duringor after cooling. Such dispersions of urea compounds D) present in theform of a finely divided, preferably crystalline solid in theepoxy-functional crosslinking agent component B) or the organic solutionthereof may also be prepared by melting and finely distributing the ureacompounds D) in B) and subsequently cooling below the solidification ormelting point of the urea compounds D).

It may be advantageous if acid is present in the reaction system duringthe preparation of the urea compounds D) from amine and polyisocyanatecompounds, which takes place in the presence of epoxy-functionalcrosslinking agent component B) as such or in the organic solutionthereof. The content of acid in the reaction medium is then, forexample, from 0 to less than 20 mg of KOH/g, based on the resin solidsin the reaction medium. Inorganic or organic acids, preferablycarboxylic acids, may be used as acids for adjusting the acid number toa value within the indicated range. It is preferred to usecarboxyl-functional binder of component A) for adjusting the acid numberin the reaction medium. The reaction medium then containsepoxy-functional component(s) B), an appropriate amount ofcarboxyl-functional component(s) A) for adjusting its acid value in therange indicated above and, optionally, organic solvents.

The content of urea compounds D) in the dispersions of D), B) and,optionally, solvent is generally from 0.5 to 10 wt. %, for example from1 to 10 wt. %, based on the solids content of epoxy-functionalcrosslinking agent component B).

The coating compositions according to the invention are preferablyprepared by mixing the dispersion of the urea compounds D) in the liquidor organically dissolved epoxy-functional crosslinking agent componentB) with the other constituents of the coating composition. For example,the dispersion of the urea compounds D) is first mixed with component A)and the portion of component B) which may still be lacking, before thefurther constituents are added.

Moreover, there may be used for the coating compositions according tothe invention, for example, the urea compounds D), starting materials,processes and process parameters for their preparation and theirincorporation into coating compositions described in DE-C-27 51 761,EP-A-0 192 304 and EP-A-0 198 519.

If the coating compositions according to the invention are to be used aspigmented finishing lacquers, for example in the production of the outerfinishing layer of a multilayer lacquer coating, then they containpigments and, optionally, extenders. The pigment/resin solid weightratio is, for example, in the range from 0.05 to 2:1. Examples ofpigments are inorganic and/or organic coloured pigments and/or effectpigments, such as, for example, titanium dioxide, iron oxide pigments,carbon black, azo pigments, phthalocyanine pigments, quinacridonepigments, metallic pigments, for example of titanium, aluminium orcopper, interference pigments, such as, for example,titanium-dioxide-coated aluminium, coated mica, graphite effectpigments, lamellar iron oxide, lamellar copper phthalocyanine pigments.Examples of extenders are extenders conventionally employed in lacquers,such as, for example, talcum and silicates.

The coating compositions according to the invention which can be used aspigmented finishing lacquers or, preferably, as transparent clearlacquers may also contain additives conventionally employed in lacquersin amounts conventionally employed in lacquers, for example up to 5 wt.%, based on the total lacquer, for example transparent pigments orextenders, flow agents, colourings, light stabilisers, antioxidants, orfurther rheology-controlling agents which can be used in addition to theurea compounds D), such as microgels, NAD (=non-aqueous dispersions),compounds yielding formaldehyde at the latest during stoving, catalystsfor catalysing the reaction of carboxyl and epoxy groups and/or forcatalysing the additional crosslinking which is optionally possible.

The coating compositions according to the invention may be applied byknown processes, especially by spraying in layer thicknesses of, forexample, from 25 to 60 μm. After a vaporisation phase, the appliedcoating composition can be crosslinked by heating. The stovingtemperatures are, for example, from 60 to 180° C., preferably from 60 to160° C.

The coating compositions according to the invention may be used toproduce the outer pigmented finishing lacquer layer of a multilayerlacquer coating. In that respect, the present invention relates also tothe use of the coating compositions according to the invention asfinishing lacquer coating compositions.

The coating compositions according to the invention are preferablyformulated as transparent clear lacquers which can be used to producethe outer clear lacquer layer of a multilayer lacquer coating. In thatrespect, the present invention relates also to the use of the coatingcompositions according to the invention as clear lacquer coatingcompositions. For example, the clear lacquer coating compositionaccording to the invention may be applied to a substrate provided with acolouring and/or effect-giving single- or multi-layer pre-coating andstoved. The stoving temperatures of the clear lacquer coatingcompositions according to the invention are, for example, from 60 to160° C. For automotive applications they are, for example, from 60 to140° C., and for applications in the series lacquering of motor vehiclesthey are especially from 80 to 140° C. and preferably from 110 to 130°C.

The clear lacquer coating compositions according to the invention arepreferably used for the production of a base lacquer/clear lacquermultilayer lacquer coating. In that connection, a colouring and/oreffect-giving base lacquer layer is applied to an optionally pre-coatedsubstrate, especially to pre-coated motor vehicle bodies or partsthereof, before the clear lacquer coating layer of a clear lacquercoating composition according to the invention is applied and stoved.Examples of pre-coating on motor vehicle bodies or parts thereof are anelectrophoretic primer layer, a two-layer pre-coating consisting of anelectrophoretic primer layer and a spray filler layer, or a two-layerpre-coating consisting of an electrophoretic primer layer and a secondcoating layer applied by electrophoresis.

The colouring and/or effect-giving base lacquer layer may be stovedbefore application of the clear lacquer layer of the clear lacquercoating composition according to the invention, but the clear lacquercoating composition according to the invention is preferably applied bythe known wet-on-wet process to the base lacquer layer which determinesthe colour of the multilayer lacquer coating. In that connection, thebase lacquer layer is applied by spraying from a colouring and/oreffect-giving aqueous or solvent-based base lacquer in a dry layerthickness that is dependent on the colour, for example from 10 to 25 μm.Following application of the base lacquer layer, the clear lacquer layerof the clear lacquer coating composition according to the invention isapplied, after a brief phase of exposure to air, for example at from 20to 80° C., by spraying in a dry layer thickness of generally from 25 to50 μm. The coating may optionally be exposed to air for a short time.The substrate is then fed to the stoving process, in which the clearlacquer coating layer together with the base lacquer layer is stoved atelevated temperatures, for example from 60 to 160° C.

With the present invention it is possible to produce, especially onmotor vehicles and parts thereof, multilayer lacquer coatings,especially base lacquer/clear lacquer two-layer lacquer coatings, havingan outstanding visual aesthetic effect and good resistance to chemicalsand acids. Sagging of the clear lacquer on vertical surfaces duringcuring, especially during stoving, is effectively prevented.

EXAMPLE 1

(Preparation of a Carboxyl-functional Polyester):

a) Preparation of a hydroxyl-functional polyester oligomer:

1100 g of trimethylolpropane and 899 g of adipic acid are esterified toan acid number of 0.5 mg of KOH/g in the presence of 2 g ofhypophosphorous acid at from 180° C. to 240° C. in the melt. The mixtureis then diluted with 770 g of butyl acetate.

The product has a baking residue of 64.5 % (1 h, 150° C.) and a hydroxylnumber of 390 mg of KOH/g, based on solids content.

b) Carboxyl-functionalisation of the hydroxyl-functional polyesteroligomer:

878 g of the product of Example la), 622 g of hexahydrophthalicanhydride and 277 g of butyl acetate are heated to 80° C. When theexothermic reaction has subsided, the mixture is heated to 140° C. andthe reaction is carried out until the desired acid number is reached.100 g of epsilon-caprolactone are then added. The reaction is carriedout at 140° C. until the theoretical solids content is reached.

The carboxyl-functional polyester resin has a baking residue of 67.7 %(1 h, 150° C.) and an acid number of 190 mg of KOH/g, based on solidscontent.

Preparation of Urea Dispersions in the Presence of Epoxy-functionalMethacrylic Copolymers:

EXAMPLE 2

At room temperature, 836 g of a 69 wt. % solution of an epoxy-functionalmethacrylic copolymer (monomer weight ratio: 3% tert.-butyl acrylate,11% butanediol monoacrylate, 17% styrene, 24% ethylhexyl methacrylate,45% glycidyl methacrylate; number-average molecular weight (M_(n))=4000)in a 9:1 mixture of Solvesso 100 (mixture of aromatic hydrocarbonshaving a boiling range from 155 to 185° C.) and n-butanol are placed ina vessel, and 6.8 g of hexamethylene diisocyanate are added. Afterhomogenisation, 16.5 g of a 50 wt. % solution of benzylamine inn-butanol are metered in, with rapid stirring, in the course of 5minutes. 30 g of n-butanol are then added, and stirring is continued forone hour at room temperature. A resin solution made milky by ureacrystals is obtained.

EXAMPLE 3

At room temperature, 492 g of the 69 wt. % solution of theepoxy-functional methacrylic copolymer of Example 2, 9.6 g of thesolution of the carboxyl-functional polyester of Example 1, 24 g ofn-butanol and 42.6 g of Solvesso 100 are placed in a vessel, and 4 g ofhexamethylene diisocyanate are added. After homogenisation, 9.9 g of a50 wt. % solution of benzylamine in n-butanol are metered in, with rapidstirring, in the course of 5 minutes. 18 g of Solvesso 100 are thenadded, and stirring is continued for one hour at room temperature. Aresin solution made milky by urea crystals is obtained.

EXAMPLE 4

At room temperature, 492 g of the 69 wt. % solution of theepoxy-functional methacrylic copolymer of Example 2, 9.6 g of thesolution of the carboxyl-functional polyester of Example 1, 24 g ofn-butanol and 42.6 g of Solvesso 100 are placed in a vessel, and 5 g ofbenzylamine are added. After homogenisation, 9 g of a freshly preparedmixture of 4 g of hexamethylene diisocyanate and 5 g of n-butanol aremetered in, with rapid stirring, in the course of 5 minutes. 18 g ofSolvesso 100 are then added, and stirring is continued for one hour atroom temperature. A resin solution made milky by urea crystals isobtained.

EXAMPLE 5

At room temperature, 479 g of the 69 wt. % solution of theepoxy-functional methacrylic copolymer of Example 2, 9.6 g of thesolution of the carboxyl-functional polyester of Example 1, 24 g ofn-butanol and 46.5 g of Solvesso 100 are placed in a vessel, and 8.1 gof hexamethylene diisocyanate are added. After homogenisation, 19.8 g ofa 50 wt. % solution of benzylamine in n-butanol are metered in, withrapid stirring, in the course of 5 minutes. 13 g of Solvesso 100 arethen added, and stirring is continued for one hour at room temperature.A resin solution made milky by urea crystals is obtained.

EXAMPLE 6

At room temperature, 836 g of a 69 wt. % solution of an epoxy-functionalmethacrylic copolymer (monomer composition: 3% tert.-butyl acrylate, 11%butyl acrylate, 17% styrene, 24% ethylhexyl methacrylate, 45% glycidylmethacrylate; number-average molecular weight (M_(n))=3800) in a 9:1mixture of Solvesso 100 and n-butanol are placed in a vessel, and 6.8 gof hexamethylene diisocyanate are added. After homogenisation, 16.5 g ofa 50 wt. % solution of benzylamine in n-butanol are metered in, withrapid stirring, in the course of 5 minutes. 30 g of n-butanol are thenadded, and stirring is continued for one hour at room temperature. Aresin solution made milky by urea crystals is obtained.

EXAMPLE 7

At room temperature, 492 g of the 69 wt. % solution of theepoxy-functional methacrylic copolymer of Example 6, 9.6 g of thesolution of the carboxyl-functional polyester of Example1, 24 g ofn-butanol and 42.6 g of Solvesso 100 are placed in a vessel, and 4 g ofhexamethylene diisocyanate are added. After homogenisation, 9.9 g of a50 wt. % solution of benzylamine in n-butanol are metered in, with rapidstirring, in the course of 5 minutes. 18 g of Solvesso 100 are thenadded, and stirring is continued for one hour at room temperature. Aresin solution made milky by urea crystals is obtained.

EXAMPLES 8a-k

Production of Clear Lacquers and Production of Multilayer LacquerCoatings:

With the present invention it is possible to produce, especially onmotor vehicles and parts thereof, multilayer lacquer coatings,especially base lacquer/clear lacquer two-layer lacquer coatings, havingan outstanding visual aesthetic effect and good resistance to chemicalsand acids. Sagging of the clear lacquer on vertical surfaces duringcuring, especially during stoving, is effectively prevented.

Clear lacquers having the composition indicated in Table 1 are produced.

Metal sheets provided with a cataphoretic primer and a filler layer areeach sprayed with a black base lacquer in a dry layer thickness of 16 μmand pre-dried for 10 minutes at 80° C. Clear lacquers 8a-k are eachapplied to the hanging sheets by spraying in a wedge shape with a layerthickness gradient of from 10 to 60 pm dry layer thickness. Afterexposure to air for 5 minutes at room temperature, stoving is carriedout for 20 minutes at 140° C. (object temperature). The metal sheets arein the vertical position during all the operations.

High-gloss multilayer lacquer coatings are obtained in each case. Noneof the multilayer lacquer coatings exhibits a visible change in the film(swelling) in the drop test with 10% sulfuric acid (20 minutes, 60° C.).

As well as the composition of the clear lacquers, Table 1, also showsthe sagging limit in each case.

TABLE 1 Clear Lacquers 8 Constituents (parts by weight) a b c d e f g hi k A¹⁾ 48.9 — — — 22.5 — — — — — Resin solution of Example 2 — 52.7 — —— 57.0 — — — — Resin solution of Example 3 — — 51.8 — — — 56.0 — — —Resin solution of Example 4 — — — 54.0 — — — — — — Resin solution ofExample 5 — — — — 26.4 — — — — — Resin solution of Example 6 — — — — — —— 53.7 — 55.7 Resin solution of Example 7 — — — — — — — — 52.8 — Resinsolution of Example 1 20.2 18.7 18.1 18.9 18.6 20.2 19.5 19.1 18.5 20.1Melamine resin²⁾ 7.0 6.5 6.3 6.5 6.4 — — 5.0 5.0 — Light stabilizer³⁾ ineach case 2.0 Flow agent⁴⁾ in each case 0.5 Benzylhexiformal⁵⁾ — — — — —1.0 1.0 — — 1.0 Methoxypropanol in each case 4.5 Dipropylene glycoldimethyl in each case 2.5 ether Butanol in each case 4.5 Solvesso 1009.9 8.1 9.8 6.6 12.1 7.8 9.5 8.2 9.7 9.2 Clear lacquer sagging limit(μm) 33 >60 55 56 55 >60 55 >60 54 58 ¹⁾69 wt. % solution of the(meth)acrylic copolymer with epoxy groups of Example 2 ²⁾butylatedmelamine resin, 70 wt. % in butanol ³⁾1:1 mixture of a benxtriazolederivative and a sterically hindered amine (HALS type) ⁴⁾silicone oil⁵⁾Preventol D2 from Bayer

What is claimed is:
 1. Coating compositions containing abinder/crosslinking agent system, one or more organic solvents,anti-sagging agents and, optionally, pigments and/or extenders whereinthe binder/crosslinking agent system contains from 20 to 80 wt. % of oneor more carboxyl-functional components A) selected from the groupconsisting of carboxyl-functional (meth)acrylic copolymers,carboxyl-functional polyesters, and mixtures thereof the carboxylfunctionality of which corresponds in each case to an acid number offrom 20 to 300 mg of KOH/g, and from 20 to 80 wt. % of one or moreepoxy-functional crosslinking agents having at least two epoxy groupsper molecule B), the percentages by weight of A) and B) adding up to 100wt. %, from 0 to 30 wt. % of one or more polymer polyols C), based onthe sum of the weights of components A) and B), from 0 to 20 wt. % ofone or more further crosslinking agents E) other than A), B) and C),based on the sum of the weights of A), B) and C), from 0 to 10 wt. % ofone or more monoepoxides F), based on the sum of the weights of A) andB), and as anti-sagging agents, from 0.1 to 3 wt. %, based on the resinsolids, of one or more solid, finely divided urea compounds D) whichhave previously been prepared in the presence of at least a portion ofthe epoxy-functional crosslinking agent(s) B) and which are insoluble inthe coating composition, all percentages by weight being based in eachcase on the solids.
 2. Coating compositions according to claim 1,characterised in that the preparation of the finely divided ureacompounds D) is carried out by reacting amine and isocyanate compoundsin the presence of at least a portion of the epoxy-functionalcrosslinking agents B) and, optionally, of organic solvent.
 3. Coatingcompositions according to claim 1, characterised in that the preparationof the finely divided, solid urea compounds D) is effected by meltingand finely distributing the urea compounds D) in at least a portion ofthe crosslinking agent component B) and, optionally, of organic solvent,and subsequently cooling below the solidification or melting point ofthe urea compounds D).
 4. Coating compositions according to claim 1,characterised in that the urea compounds D) are prepared in such anamount in component B) and, optionally, solvent that the content of ureacompounds D) in the resulting dispersions is from 0.5 to 10 wt. %, basedon the solids content of epoxy-functional crosslinking agent componentB).
 5. Coating compositions according to claim 1, characterised in thatthe solid urea compounds D) have particle sizes of from 0.1 to 20 μm.